Two problems affecting world health (particularly in third world countries) are diabetes and vaccinations for disease prevention. Vaccination programs depend on the availability of syringes or hypodermics. Some diabetics face the traumatic and painful prospect of daily insulin injections. There is a need for a less painful injection alternative.
One type of needleless hypodermics are jet injectors. Such jet injectors on the market use either compressed gas or compression springs to generate a high velocity jet (diameters ranging between 76 to 360 μm) to penetrate the skin. These devices obtain fluid velocities between 80 to 190 m/s and generate up to 600 W of power. Typical delivery volumes range between 0.05 and 1 cc. To use these devices the users have to transfer the drugs from their original vials to the devices. In addition, the jet injectors typically deliver the dose in the form of a stream rather than spray. With jet injectors, a fluid pocket forms under the dermis. Backflow may result if the pressure in the pocket exceeds the flow pressure, potentially causing cross-contamination. In addition, doses delivered as a spray would be absorbed more readily than a pocket of fluid. However, jet injectors do not deliver a consistent dose; they involve multi-step processes to use; they induce pain (due to the high pressure); and are susceptible to cross-contamination during transfer. Thus, the devices on the market are typically designed as single-use devices usually used by individuals to avoid anaphylactic or insulin shock. That is, individuals pre-load the devices and carry them around in case of an emergency situation.
In order to avoid the shortcomings of jet injectors, some developers of needleless hypodermics have looked to electrospray technology. Issued U.S. Pat. No. 6,093,557 discloses a method for electrostatically creating a spray of charged particles for delivery into cells. Issued U.S. Pat. No. 4,945,050 discloses a method for electrostatically accelerating particles into cells.